1. Field of the Invention
The present invention relates to a method for message transmission and related communication device in a wireless communication system, and more particularly, to a method and related communication device of the wireless communication system for managing notification message reception corresponding to natural disaster warning.
2. Description of the Prior Art
Earthquake and Tsunami Warning System (ETWS), set forth by the 3rd Generation Partnership Project (3GPP), is a natural disaster warning system for delivering Warning Notification simultaneously to many mobile users who should evacuate from approaching Earthquake or Tsunami. The ETWS consists of a PLMN (Public Land Mobile Network) that is capable to deliver Warning Notification and user equipments (UEs) that are capable to receive Warning Notification. The PLMN of the ETWS can be a GERAN (GSM/EDEG radio access network) of a 2G/2.5G GSM system, a UTRAN (UMTS radio access network) of a 3G UMTS system, or a EUTRAN (evolved-UTAN) of a long term evolution (LTE) system. Warning Notification Providers, which are usually run by local governments, produce Warning Notification to PLMN operator when an earthquake or tsunami event occurs.
Warning Notification is classified into two types depending on the purpose and urgency of the notification. The first type of Notification is called Primary Notification that delivers the most important information of the threat that is approaching to users (e.g. the imminent occurrence of Earthquake or Tsunami) and shall be delivered to the users as soon as possible. The second type of Notification is called Secondary Notification that delivers additional information, such as instructions on what to do or where to get help.
The Warning Notification Provider publishes a Primary Notification to PLMN and specifies the Notification Area where the Warning Notification is expected to be distributed when occurrence of a natural disaster is detected. Single or multiple Secondary Notifications are published following the Primary Notification. Finally, the Warning Notification Provider may request dissemination of notification to the PLMN to stop.
According to the prior art specification, the GERAN, the UTRAN, or the EUTRAN can use paging message to send a primary notification message since the primary notification message shall be delivered to the UE within 4 seconds. Alternatively, system information is utilized to send the primary notification message, and a paging message is then sent to notify UE to receive the primary notification message by receiving the broadcasted system information in a serving cell. As for delivery of a secondary notification message, Broadcast/Multicast Control (BMC) is used in the UTRAN, system information is used in the EUTRAN, and SMS-CB (Short Message Service-Cell Broadcast) is used in GERAN.
In the prior art, an ETWS capable UE in an idle mode starts to receive the secondary notification messages once one or more primary notification messages are received. However, the prior art neither specifies when the ETWS capable UE shall stop receiving the secondary notification messages if the warning notification providers stop delivering secondary notification messages nor specifies UE reactions to secondary notification message reception when cell selection or reselection, out of service, a RAT (Radio Access Technology) change, and other situation occurs. The main drawback is that the UE power drains if the UE cannot stop receiving secondary notification messages when no secondary notification message is delivered. Some examples are provided below to illustrate the drawback.
Issue 1 is described in this paragraph. The UE receives a paging message including a primary notification message from a warning notification provider in a GREAN cell. The UE starts to receive cell broadcast (CB) messages including secondary notification messages by listening to CBCH (Cell Broadcast Channel). After a while, the warning notification provider stops delivering the secondary notification messages. However, the UE still keeps receiving CB messages on CBCH.
Issue 2 is described in this paragraph. The UE receives a paging message including a primary notification message from a warning notification provider in a UTRAN cell. The UE starts to receive cell broadcast (CB) messages including secondary notification messages by listening to SCCPCH (Secondary Common Control Physical Channel). After a while, the warning notification provider stops delivering the secondary notification messages. However, the UE still keeps receiving CB messages on SCCPCH.
Issue 3 is described in this paragraph. The UE receives a paging message including a primary notification message from a warning notification provider in a EUTRAN cell. The UE starts to receive system information message including secondary notification messages. After a while, the warning notification provider stops delivering the secondary notification messages. However, the UE still keeps receiving system information.
Issue 4 is described in this paragraph. After the UE receives a primary notification message and then enters RR (radio resource) dedicated mode or a packet transfer mode in a GERAN cell or RRC (radio resource control) connected mode in a UTRAN/EUTRAN cell due to a MT (Mobile Terminated) call or web browsing, the UE cannot receive the secondary notification messages. When the UE enters the idle mode, the prior art does not specify if the UE continues to receive secondary notification messages or not. If the base station (GERAN/UTRAN/EUTRAN) has stopped sending secondary notification messages but the UE keeps secondary notification message reception, the UE power drains.
Issue 5 is described in this paragraph. After the UE receives a primary notification message in a cell with a certain RAT (RAT 1) and then suddenly detects out of service, the UE cannot receive the secondary notification messages. When the UE re-enters in service area in the same RAT (RAT 1), the prior art does not specify if the UE continues to receive secondary notification messages or not. If the base station (GERAN/UTRAN/EUTRAN) has stopped sending secondary notification messages but the UE keeps the secondary notification message reception, the UE power drains. When the UE re-enters in service area in a different RAT (RAT 2), the prior art does not specify if the UE continues to receive secondary notification messages or not. The secondary notification messages may not be sent in the RAT (RAT 2). As a result, the UE power drains since the UE keeps receiving secondary notification messages.
Issue 6 is described in this paragraph. After the UE receives a primary notification message in a cell and then reselects to another cell before starting to receive secondary notification messages, the prior art not specify if the UE continues to receive secondary notification messages or not. If the reselected cell belongs to a different RAT, the secondary notification messages may not be sent. If the UE keeps receiving secondary notification messages, the UE power drains.
Issue 7 is described in this paragraph. The UE may miss primary notification messages (e.g. paging messages) due to cell reselection or a short interruption of service (e.g. entering elevator). In this case, the UE will not receive secondary notification messages after reselecting or re-entering the service area until the UE receives a primary notification message.
Issue 8 is described in this paragraph. The prior art does not specify how the warning notification provider only sends primary notification messages, i.e. no secondary notification message.
Issue 9 is described in this paragraph. The UE may not be able to receive paging and secondary notification messages simultaneously. For example, the reception of paging message has higher priority than normal CB (cell broadcast) messages in the GERAN/UTRAN. However, this specification may not be proper for CB messages including secondary notification messages because the secondary notification messages may contain more important information.
Issue 10 is described in this paragraph. A UE camps on a cell that the system information does not have configuration for secondary notification message. The warning notification provider requests to activate ETWS and provides primary notification and secondary notification messages. The base station controlling the cell changes system information to include configuration for UE to receive secondary notification messages. The base station sends a system information change notification message to notify UEs system information changed. The UE receives the changed system information. The base station sends a primary notification message. The UE receives a primary notification message and then receives secondary notification messages. This delivery is not efficient because the base station has to send a system information change notification message in advance of the primary notification message.
Issue 11 is described in this paragraph. The LTE base station, i.e. eNB, may not have good support for ETWS in the first launch. If paging is used to send primary notification messages, the primary notification message is easily introduced into a paging message by doing a little modification to the paging message. However, it needs more effort to support secondary notification messages. Another example is that LTE cells with a small bandwidth (e.g. 1.25 MHz) may have insufficient resources to send the secondary notification messages.